Cathode-ray tube beam sweep oscillator



Sept. 27, 1960 R. c. WILSON ETAL 2,954,533

cATHoDE-RAY TUBE BEAM SWEEP osCILLAToR Original Filed Sept. 22, 1954 2` rmx .of-fz. "-6

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fcATHonn-RAYTUBE BEAM swf-EEP osciL-LA'roR Rex C. Wilson, Glenview, and Howard Van l'epmond, Evanston, Ill., assignors, .by mesne assignments, to Hazeltine Research, =Inc., Chicago, Ill., a corporation of Illinois F(lollllixluation pf application Ser. No. 457,724, Sept. 22, .19.54. This application July 2, 1958, Ser. No. 746,115

12 Claims. (Cl. 331-147) General The present vinvention relates to an improved sweep oscillator which is adapted to energize the deection coil of a cathode-ray tube and is particularly suitable for use as the vertical sweep oscillator for a low voltage television receiver.

This application is a continuation of application Serial No. 457,724, led September 22, 1954, and entitled Cathode Ray Tube Beam Sweep Oscillator, now abandloned.

In the manufacture of television receivers for home use :it is particularly ldesirable to :operate the vreceiver `at, say, *150 volts D..fC By so doing `it "is :possible to dispense -avith the power'trafnsformer, to operate-the entirereceiver 4.from Aa single `source of :D.C. voltage without .step-down resistors, and vachieve other advantages. Difficulties have been encountered, however, in designing such .receivers because the verticalsweep oscillators requiremore than comparatively low D.C. voltage available dn the -absence of .a higher voltage source.

'In laccordance with the present invention, an improved vertical sweep .oscillator is achieved which provides ade- -quate vertical sweep power when operated at low D.C. voltage, such :as 125 volts, and yet doesnot-requireexcessive driving power. In brief, 4-theoscillatorconsists of Ia tetrode electron tube, such as a 25L6, having its anode and 4screengridconnected to the source ,of D.C. voltage through a transformerto deiine .an-oscillatory lcircuit-n 4conjunction with the cathode. A negative feedback circuit is defined in connection with the control Vgrid :by-a ycapacitance networkconnected to the anode and-control grid, which networkis charged during positive excursions zofgtheanode and .thereafter discharges through ,a .suitable resistance to Vgive the increasing current flow required to sweep the ray beam progressively across the viewing screen. Negative synchronizing pulses are .applied to the Ascreen .grid through the transformer winding vto .trigger 'the oscillator.

In operation, the negative synchronizing pulses Ydecrease the screen voltageto precipitatean` increased anode voltage whichfis fedrback :through'the ltransformer to the screen :grid to .cause ra further negative vscreen voltage swing. This feedback eifectgives a progressive and steep negative voltage swing `t-o the screen grid until it loses its -control over ithe anode current, at which -time-the direction of swing reverses `and the anode voltage swings in `the negative direction. .'During the positive lswing of 'fthe anode voltage the `.feedback rcapacitors'to lthe control atent grid :are charged by the control grid eurrentrtlowfwhich .charging occurs through ythelow time-constant charging circuit and the control grid cathode space path. Upon the negative l.swingof lthe anode, this-low time-constant circuit is broken v-so that the capacitors can discharge only through :the "longer time-constant circuitprovided ffor-.the purpose.

:When the control y grid .swingsI negativelyv in response to the negative anode voltage swing, the .screen grid `"loses ice control .of anode .current and the .control grid -ta'kes control. Flhus, .once `the `capacitor Vcharging cycle `started by the synchronizing pulse `is completed, the anode current Luniformly rises under .the control of the discharging eapacitors in thecontrol grid circuit.

An :additional feature of .the oscillator Aof .the present invention resides inthe `fact that the .synchronizing pulses are applied to lthescreen .grid in .such la fashion that voltage variations .on .the screen grid .are .not fed -baclcinto the synchronizing 4pulse source. This 'is :believed .to :be due to the connection .of the Isynchronizing pulse source through vthe transformer vto -the Y:screen grid so that :the transformer isolates the pulse .source ,from thelargevolt- Vage swings lof rtheloscillator itself. Inradditiom dav-this ar rangement the oscillator itself `serves as Aa synchronizing tpulse :separator so '-thatrboth vertical and horizontal lpulses ,may rb e applied 'without `separating circuits.

lt is, therefore, .a general object .offthe present ,invenation :to provide an improved oscillator :for .a .cathode-ray :tulle 'Sweep l Coil which :operates `.effectively at low D.C. voltage.

Another object .of the present `invention :isito provide an improved oscillator for a cathode-ray tube sweep vcoil which ldoes not feed .hack into the synchronizing .supply rcuts.

Another object of the present invention is to providea sweeposcillator `:forthevertical:sweepcoils of a cathoderay tube which can-be triggered by thefcompositeunsegiregated vertical l.and horizontal synchronizingpulse wave.

Yet another,obieet-Qfthopresentjinvention .is:.to:provide an improved oscillator for generating saw-tooth waves that is especially suitable for operation on low voltage @and employs -but a vsingle electron=discharge device or tube.

,A Vfurther and Aadditional object .of .the .present `invention is to `provide yan improved .oscillator .-for energizing a ,cathode-ray tube sweep in which ithe'magnitudeof the oscillations can ,be readilycontrolled without adversely ,aficting the wave form and in which the .recovery of control grid voltage can likewise be ,adjusted to achieve a `positive lo -ng of the Oscillator .under the ycontrol of Vthe synchronizinsrpulses.

lAnother and further-.object of :the present invention is to provide an oscillator :of Vthe above .type which gencrates .a ,linear .sweep .current wave suitable for reproduction .of an undistortfd: television image.

rIn :accordance .with a particular form ,of'lthe invention, an oscillator for ,generating as aw-.tooth wavecomprises `fan.electron-discharge de\ fice,eiectively havingarcathode, a controlelectrode, a sereenlelect-rode, and ananode, and

.means .for .biasing lthe anode and screen electrodes ina `predetermined relation to the cathode. The oscillator .alsoincludes networkmeans coupled;l to theanodescreen electrode, cathode, and theaforesaidbiasing means .and defining therewith an voscillatory vsystem having positive feedback. The oscillator Yfurther `includes a lfeed-back Vnetwork coupled to theaforesaid controlelectrode and system -for developing forthe latterduring trace portions of the saw-tooth wave negative `feedback which overbalances the positivefeedback-during theforesaid trace portions.

Also in accordance `with the invention, an oscillator vfor generating a sawrtooth .wave comprises an electron ,coupled to lthe anode, screen electrode, and cathode and defining therewith an oscillatory system having a natural period short compared .with the ,period of .the saw- `tooth wave and "having suicien-t positive feedback so the cathode.

that in the yabsence of other feedback an oscillation r-ap idly builds up until the anode-cathode current is interrupted. The oscillator further includes coupling -means coupled to the control electr-ode and oscillatory system land providing negative feedback overbalancing the positive feedback when the control electrode-cathode path in the tube is not conducting and no substantial feedback when the path is conducting. FI'lte aforesaid coupling means includes a condenser which is rapidly charged by currentA flowing through the control electrode-cathode path When the anode-cathode current isbeing interrupted and thereafter renders the control electrode negative relative to the cathode. The oscillator additionally includes resistance means coupled tothe condenser for discharging it at a relatively slow rate, whereby the potential of the control electrode gradually rises relative to that of `the cathode and causes anode-cathode current to rise until the aforesaid path again becomes conductive and the cycle of the wave is completed;

VThe novel features which we believe to be characteristic of our invention are set forth with particularity -in the appended claims. Our invention itself, however, both vas to its organization `and method of operation, together Ywith further objects and advantages thereof, will best be understood by reference to the following description Vtaken in connection with the accompanying drawing, in `which:

Fig. lis a schematic circuit diagram showing an oscillator constructed in accordance with the present invention;

Fig.V 2 is a diagrammatic representation of the wave forms in the oscillator of Fig. 1, and

Fig. 3 is a fragmentary schematic circuit diagram of lan alternative embodiment of the present invention.

Description of Fig. 1 oscillator Referring now to Fig. l, there is shown at an electron-discharge device or tube effectively having -a cathvode 10a, a control electrode 10b, la screen grid 10c, and

prising the windings 14a and 14b of the transformer 14,

respectively, which bias the anode and screen electrodes in a predetermined or positive relation to the cathode, whereby current normally ilows between the anode `and These windings are poled so that rising anode current in the positive direction in winding 14a gives rise to positive voltage at the -screen grid 10c, thus forming a positive feedback system including the cathode 10a, the screen grid 10c, and the anode 10d. Y

The capacitor 16 serves to maintain a constant unidirectional voltage at the source side of the windings 14a and 14b. However, resistances 18 and 20 permit some excursions from this condition at the actual winding terminals. This is important in the case of the winding 14h since-as hereafter describedthe synchronizing wave is applied to the tube 10 through this winding.

The vertical deflection coils of the cathode-ray tubeshown diagramm-atically at 22-are connected to the tertiary winding 14e ofthe transformer 14. Since, as is described in detail hereafter', the cu-rrent liow inwindings 14a and 1417 is rapidly changing, a correspondingly changing voltage wave is induced in winding 14C and the requisite sweep current Wave flows through the vertical deection coils. 'These coils straddle the neck of the cathode-ray tube in usual fashion and deflect the ray beam from its axial direction of travel to an extent determined by the value of the current.

Capacitors 24 and 26, acting in conjunction with resisters 28 and 30 and potentiometer 32, form a negative feedback circuit from the anode 10d to the control grid 10b. This path extends through variable resistance 34.

As described hereafter, this feedbackpath serves to swing $14. "The circuit by which this is accomplished can Vbe traced from source 36 through capacitor 42 to the screen VWinding 14b.

In a'conventional television receiver, the synchronizing source 36V consists of the first detector, local oscillator and intermediate-frequency ampliiiers which feed the second detector. Thel latter applies the complex video wave to suitable cutoff amplifiers which' discard the picture component of the signal and pass only the horizontal and ver-ticalsynchronizing components. The resultant signal consists of vertical synchronizing pulses with a repetition rate of 60 per second and horizontal synchronizing pulses with a repetition rate of about 15,000 per second. These pulses are of substantially the same magnitude but the duration of the vertical synchronizing pulses is many times greater than the duration of each 'horizontal synchronizing pulse. As described hereafter, the circuit herein'described may serve by its own inherent action to separate these two types of synchronizing pulses.

Operation of Fig. 1 circuit The practical operation of the above-described apparatus will best be evident from an examination of the wave forms shown in Fig. 2. This figure shows the wave forms on a common time scale, but not otherwise to scale.

' The negative synchronizing pulses both horizontal and lvertical from source 36 appear at capacitor 42. How- .with a 60 cycle repetition rate and comparatively long durations-do reach the screen grid 10c yand thereby cause the sharp negative voltage swing which triggers the oscillatorrto execute `a cycle of operation.

Once vthe voltage of screen grid 10c begins to fall due to the vertical ysynchronizing pulse, the positive feedback due to transformer 14 gives rise to an increasing screen grid voltage fall which is. continued until the anode current is cut olf. This action is due to the fact that the decreased anode current due to the falling screen grid voltage passes through the winding 14a. Upon anode current cutoff, the magnetic field in transformer 14 collapses at a rate determined by its natural frequency to :induce a voltage in winding 14b which drives the voltage Vsgl further in the negative direction, thus completing the positive feedback cycle and causing buildup of the swing started by the synchronizing pulse.

The positive voltage pulse of 4the anode due to the anode-current fall is applied to the control grid 10b through capacitors 24 and 26. However, as soon as the control electrode 10b swings positive in relation to the cathode 10a the control electrode conducts'current and thus holds its own voltage very close to the cathode potential. The capacitors 24 and 26 thus charge through the circuit extending from the anode 10d .through the capacito-rs in series to the control grid 10b and thence to the cathode 10a. Ars resistance 34 is comparatively small (that is, less than a megohm) the time constant of this charging circuit is short. Y

It will be noted that capacitors 26 and 24 act as a capacitance voltage divider. The former may, for example, be about 0.0022 microfarad and the latter about 0.022 rnicrofarad. Thus capacitor 26 experiences most of the voltage rise during the period the. yanode 10d isv swinging in the positive direction.

As the anode d swings positively and the .screen 10c swings negatively, the ability of the screen to control the anode space current decreases until iinally a. point is reached wherein control is lost. At this time the anode voltage Vp continues to swing in a positive direction due to collapsing elds and the screen voltage continues to swing in the negative direction until the coilapsing elds have dissipated their energy in a half cycle of oscillation at natural period of circuit, which period is short compared with the period .of the` saw-tooth wave developed for application to coils '22.

As the .anode voltage Vjp swings su'icientlyin the nega tive .direction near the .end .of the self-oscillatory half cycle, the control electrode 10b par-.takes of the negative swing and moves negatively in relation to the cathode 10a. This. isdueio the fact that at this timecontrol ,grid current ceases, so that the short timeconstant charging circuit through the `control electrode 10b is discontinued. The charge on capacitors 24 and 26 accordingly does not `change rapidly and the control electrode executes arapd and `large negative voltage .swing as .shown by the curve Vg, Fig. 2.

During the negative swing of .the control electrode 10b 'it takes control of .the .space current to the anode 10d. In other words, when the control electrode voltage 4is .in the very negative region of Fig. v2. the voltage of the screen electrode 10c does not signicantly affect 4the cathode-anode space current. At this time, therefore, the system composed of the .anode 10d, transformer 14., .and screen electrode 10c is no longer oscillatory .and .the rapid yoltage swing at the anode 10d and the .control .electrode 10b is arrested. The screen voltage VSE .accordingly tapers out from the rapid rise as shown by the curve Vsg, Fig. 2, and rises thereafter only at a relatively Aslow rate. The developed negative .feedback may therefore .be said to overbalance the positive feedback .dwingt-he .trace portions of the ,generated wave.

At the completion ofthe .negative .swing of the .anode voltage Vp, the control electrode .10b has a negative potential due to the charge on capacitors .26 and 24. Iltis charge, particularly that on the .capacitor 26., leaks .off through resistors 28, 30., and 32, -thus .causing .the control electrode voltage to increase slowly .and the anode current ilkewise to increase slowly .as shown by thecurves of Fig. 2. The anode potential Vp likewise :decreases slowly as shown by the curve Vp, Fig. .2.

By the time the next vertical synchronizing pulse .is applied, the control electrode voltage Vg .has .risen `.to .a value wherein it no longer defeats .the control exerted by the screen 10c over the .anode space current. Hence, `the .application of the synchronizing pulse through .the screen winding l4b .to the screen lcidecreases .the anode space .current to give .rise to thecycle of olgmarations` above described.

The potentiometer 32 serves as a hold .control to assnre that .the oscillator executes ,one-cyclein .response to each synchronizing pulse. Alternatively, resistance 30 may be made variable for this purpose. In either event the rate of discharge of capacitors 24 and 26 is controlled so .that the oscillator is conditioned to receive a new synchronizing pulse when .each pulse arrives. Adjustment of potentiometer 32 ,(.orr resistance 3.0) accordingly fixes the voltage .of control .electrode 10b .at the .instant .the synchronizing pulse is applied through winding 14b to the screen 10c. It can .accordingly be adjusted toessure lthat the tube 10 .is in .condition Yto respond toeach Asynchronizing pulse.

The resistance 2.8 combines with capacitor 24 to .the voltage .across .capacitorl .andresistances 30 :and 32 .during the time .the :capacitor .26 .is discharging. .affords .control-of.the,1inearity .of .the rising .current wave to .anode .10d to .overcome the tendency of .this portion .of .the wave .to depart from linearity.

4The capacitors 48 and 50 form a capacitance voltage y.

divider whichfeeds voltage to the cathode-ray tube blanking circuit 52. In brief, this circuit applies pulses from the wave V58 to the control grid of the cathode-ray tube to interrupt the ray beam during the .time vertical retrace is in effect. This structure is disclosed and claimed in our United States 'Patent No. 2,760,108.

One of the features of the present invention 'lies inthe fact that the negative synchronizing source 36 is not subjected to high voltages fed back from the oscillator. This is believed to be due to the fact that the synchronizing pulse voltage .is applied .to the screen grid 10c through the 'winding 1412. Since most of the screen grid voltage swing appears across this winding, the winding serves by its presence to isolate the capacitor 42-and hence the synchronizing source --from these voltage excursions. Were it not for this isolating action, the

synchronizing ,circuit would be required to withstand the 'Y 'eiects .o f the large screen .grid voltage swings and it would be necessary to provide isolating .circuits `,for purpose.

If desired, the .resistance 18 may be made variable to control the vpositive lpotential onscreen grid 10c. This controls the negative voltage .swing .of control .electrode `10b and hence the extent .of the current changes .during the sweep oscillation. It thus varies .the extent .of the cathoderay Ybeam 2sweep .and the 4size of the picture.

Since the required sweep cur-rent ow increases as the picture brightness .is decreased, it is desirable to vary the .extent of the ray beam deflection current swings with the intensity of the beam. This is accomplished in the circuit of Fig. 1 by the resistance 54 whichin conjunction with `the 'brightness control potentiometer 56-varies the .bias potential at screen, grid 1.0L` in accordance with the .brightness of the picture, thus compensating for adjustment of such brightness. The potentiometer .56 .controls the brightness of the picture by vreason of its connection through resistance S8 to the cathode of cathode-ray lube, so that increased positive potential at fthe movable vterminal of the potentiometer 56 decreases .the picture brightness and simultaneously increases the .amplitude orf the sweep .current wave applied to the vertical deection coils 22.

AIn an actual ltelevision receiver with an anode supply voltage source of only volts and a 21-inchcathoderay picture tube, the following circuit values .were used 'in the circuit of Fig. l:

'Tu-be 10 Type 25L6. Resistance 18 18,000 to 68,000 ohms. Capacitor 16 10 microfarads. Potentiometer 32 97,000 ohms. 'Resistance 20 1,800 ohms. Capacitor 42 0.22 .microfarads Capacitor 48 0.01 microfarads. .Capacitor 50 0.022 microfarads. Resistance 38 47,000 ohms. Resistance 30 2.2 megohms. Resistance 34 390,000 to 640,000 ohms. Capacitor 26 0.0022 microfarads. Capacitor 24 0.022 rnicrofarads. Resistance 28 1.8 megohms. Transformer 14:

Anode winding 14a 10,000 ohms at `60 cycles with l0 milliarnperes 'll-C. 'Screen winding 14b One-third the turns of the anode winding 14a.

Tertiary winding 14c "One twenty-fourth -the turns .of the anode winding 14a.

It has been found that the oscillator of 4the present vinvention triggers effectively and reliably if fed with the composite synchronizing wave including both the horizontal and the vertical pulses. It is thus possible to zuse this oscillator .in a .television -receiver lwithout such integrating network and thereby simplify the receiver' and ,avoidthe expense of providing suchY network. This action of the oscillator is believed to be due to thefeffecytiveness of screen ywinding 14a of the transformer 14 in ,passing'onl'ythe relatively low-frequency broad 60-cycle vertical synchronizing pulses while not passing the relatively high-frequency sharp horizontal synchronizing pulses. The oscillatorthus by its own inherent action serves as an integrating synchronizing pulse-separating jdevice. L Y f It should further be noted that since the, synchronizing pulse source need not include an integrating device, the Aloss in signallevel -necessarily attendant upon the use of such device is avoided.

Description of Fig. 3 'circuit In the alternative construction o f Fig. 3, the diode 44 vhas its anode 44a connected to the controlv electrode `10b ofthe tube I and its. cathode 44h connected to the negative terminal 46a ofthe bias voltage source 46. Since the cathode 44b of the diode is negatively biased in relation to the anode 44a, the diode conducts unless the control electrode 10b of the tube 10 is biased negatively by approximately the voltage of bias source 46. With the circuit of Fig. 3 it is accordingly vpossible to control the extent the control electrode 10b can swing in the positive direction, including a control holding this electrode negative at all times. The operation of the circuit of Fig. 3 is like that of Fig. 1 except that the diode 44 conducts rather than the control electrode-cathode path of the tube 10.

' While we have shown and describedspecic embodimentsl of the present invention it will be understood that ,numerous modifications and alternative constructions may be made without departing from the true spirit and scope thereof. vWe therefore by the following claims intend to cover all such modifications and alternative constructions as fall within their true spirit and scope.

What is claimed is: I

l. A sweep oscillator for a cathode-ray tube comprising: a current-control `device including a current-emitting electrode, a current-receiving electrode, and iirst and second control electrodes; means for `applying negative synchronizing pulses to said second control electrode; means coupling said current-receiving and second control electrodes for driving the former positive Aand the latter negative responsive to said synchronizing pulses; means coupling said current-receiving and iiirst control electrodes land responsive to the positive lexcursion of the former for causing the latter to draw current from said current-emitting electrode; means responsive to the latter current for `driving said iirst control electrode negative and then slowly positive; and means responsive to the current to said current-receiving electrode as said first control electrode goes slowly positive for deriving ya sweep voltage. f

2. A ysweep oscillator for a cathode-ray tube comprising: akcurrent-control device including a current-emitting electrode, a current-receiving electrode, and rst and second control electrodes; means for `applying periodic negative synchronizing pulses -to said second control electrode; means coupling said current-receiving and second control electrodes for driving the former positive and theV latter negative responsive to lsaid synchronizing pulses; means coupling said current-receiving and rst control electrodes and responsive to the positive eX- ing: `an electron tube including va cathode, an anode, -a screen grid, and a control grid; means for applying periodic negative synchronizing pulses to said screen grid; means coupling said anode andscreen grid for driving the'anode positive and the screen grid negative responsive to said synchronizing pulses; means coupling said anode vand control grid :and responsive to the positive excursion of the anode for causing the control grid to ldraw current from said cathode; means including a resistance-capacitance network chargeable by the latter current for driving said control grid negative and then slowly positive synchronously with said synchronizing pulses; and means responsive to' thecurrent to said anode as said control grid goes slowly postivefor deriving a sweep voltage. 4. A linear.v sweep oscillator for a cathode-ray tube beam-deection coil comprising in combination: an electron tube having cathode, control, screen, and anode electrodes; means to supply positive bias voltage to the cursion of the former for causing the latter to ldraw current from said current-emitting electrode; means including la resistance-capacitance network chargeable by the latter current for driving said first control electrode negative :and then slowly positive symchronously with said synchronizing pulses; and means responsive -to the lcurrent to said current-receiving electrode as said first con- -trol electrode goes slowly positive for deriving a sweep voltage.V

3. A sweep oscillator for a cathode-ray tube comprisanode and screen electrodes, respectively, in relation to the cathode electrode; `a transformer having an anode winding interposed between the anode electrode Iand said means and a screen winding interposed between the screen electrode and said means, said windings being in positive feedback relation to define an oscillatory system including the cathode,.screen, land anode electrodes; `a

-pair of series capacitors connecting the anode and control electrodes; means dening a discharge path for the 4capacitors including resistance means connecting the control electrode to the cathode electrode and resistance means connecting the junction of the series capacitors to fthe cathode electrode; and means to apply negative synchronizing pulses through the screen winding to the screen electrode. 5. A linear sweep oscillator Ifor `a cathode-raytube Ibeam-deflection coil comprising in combination: an electron 'tube having cathode, control, screen, and anode electrodes; means to supply positive bias voltage to the anode and screen electrodes, respectively, in relation to the cathode electrode; a transformer having Ian anode winding interposed between the anode electrode and said means and `a screen winding interposed between the screen electrode yand said means, said windings being in positive feedback relation to dene an oscillatory system 'including the cathode, screen, `and `anode electrodes; a pair of series capacitors connecting the anode and control electrodes, one of said capacitors being relatively small in relation to the other and being connected to the control electrode so Ithat most of the capacitor voltage appears between the junction of the capacitors and the control electrode; means defining a Idischarge path for the capacitors including resistance means connecting the control electrode to -the cathode electrode and resistance means connecting the junction of the series capacitors to the cathode electrode; .and means -to apply negative synchronizing pulses through the screen winding to the screen electrode. i

' 6. An oscillator for generating a saw-tooth Wave comprising: an electron-discharge device eifectively having a cathode, la control electrode, a screen electrode, and an anode; means for bia-sing said anode and screen electrode in a predetermined relationto said cathode; network 'means coupled to'said anode, screen electrode, cathode, and biasing means land defining therewith an oscillatory system having positive feedback between said lanode and screen electrode; and .a feedback network, including a condenser coupled to said control electrode and said anode and operative to drive the control electrodecaithode path of ysaid device to conduction during the negative build-up of voltage on said screen electrode and including a `discharge path for said'condenser having a time constant longer than thatof the screen electrode :build-up interval, for developing for said system during trace port-ions of said wave negative feedback which overbalances said positive feedback during said trace portions.A f

'7'. oscillator4 foige'reratingr a saw-tooth wave comprising: an electron-discharge device effectively havingl 4a cathode, a control electrode, a screen electrode, andan anode; means for biasing said anode and screen electrode in a predetermined relation to said cathode; network means coupled to s aid anode, screen electrode, cathode, 'and biasing means and defining therewith an oscillatory system having positive feedback between said anode and screen electrode; and a feedback network, including a pair of Series-connected condensers coupled between said controlh electrode and said anode, resistance means coupled between said controlelectrodeand said cathode, and,V resistance means connected between the junction` of said condensers and said cathode, Ifor developing for said system during trace portions of said wave negative feedback which overbalances said positive feedback during said trace portions.

8. An oscillator for generating a saw-tooth 4wave comprising: an electron tube having a cathode, a control electrode, a screen electrode, and an anode; means biasing said anode and screen electrode positively in relation to said cathode whereby current normally flows between said anode and cathode; network means coupled to said anode, screen electrode, and cathode and defining therewith an oscillatory system having a natural period short compared with the period of said wave and having sufficient positive feedback between said anode and screen electrode so that in the yabsence of other feedback an oscillation rapidly builds up until said anode-cathode current is interrupted; coupling means coupled to said control electrode and oscillatory system and providing negative feedback overbalancing said positive feedback when the control electrode-cathode path in said tube is not conducting and no substantial feedback when said path is conducting, said coupling means including a condenser which is rapidly charged by current flowing through said path when Said anode-cathode current is being interrupted aud thereafter renders said control electrode negative relative to said cathode; and resistance means coupled to said condenser for discharging it at a relatively slow rate, whereby the potential of said control electrode gradually rises relative to that of said cathode and causes said anode-cathode current to rise until said path again becomes conductive and the cycle of said wave is completed.

9. An oscillator for generating a saw-tooth wave comprising: an electron tube having a cathode, a control electrode, a screen electrode, and an anode; means biasing said anode and screen electrode positively in relation to said cathode whereby current normally flows between said anode and cathode; network means coupled to said anode, screen electrode, and cathode and defining therewith an oscillatory system having a natural period short compared with the period of said wave and having suffcient positive feedback between said anode and screen electrode so that in the absence of other feedback an oscillation rapidly builds up until said anode-cathode current is interrupted; coupling means coupled to said control electrode and oscillatory system and providing negative feedback between said anode and control electrode overbalancing said positive feedback when the control electrode-cathode path in said tube is not conducting and no substantial feedback when said path is conducting, said coupling means including a condenser which is rapidly charged by current flowing through said path when said anode-cathode current is being interrupted and thereafter renders said control electrode negative relative to said cathode; resistance means coupled to said condenser for discharging it at a relatively slow rate, whereby the potential of said control electrode gradually rises relative to that of said cathode and causes said anode-cathode current to rise until said path again becomes conductive and the cycle of said wave is completed; and means coupled to said control electrode for causing said path to be conducting in the absence of oscillation whereby oscillation is initiated.

I0.` An oscillator for generating a saw-tooth wave comprising: an electron tube having a cathode, a control electrode, a screen electrode, and an anode; means biasing said anode and screen electrode positively in relation to said cathode whereby current normally flows between said anode. and cathode; network means coupled to said anode, screen electrode,A and cathode and defining therewith an oscillatory system having a natural period short compared with thefperi'od' oi.A said wave and having sufficient positive feedback between said anode and screen electrode so that in the absence of other feedback an oscillation rapidly builds up until said anode-cathode current is interrupted; coupling means coupled to said control electrode and oscillatory system and providing negative feedback between said anode and control electrode overbalancing said positive feedback when the control electrode-cathode path in said tube is not conducting and no substantial feedback when said path is conducting, said coupling means including a condenser which is rapidly charged by current owing through said path when said .anode-cathode current is being interrupted and thereafter renders said control electrode negative relative to said cathode; resistance means coupled to said condenser for discharging it at a relatively slow rate, whereby the potential of said control electrode gradually rises relative to that of said cathode and causes said anode-cathode current to rise; and means for applying control pulses to said oscillatory system to render said path conducting, whereby the cycle of said saw-tooth wave is completed.

11. An oscillator for generating a saw-tooth wave cornprising: an electron tube having a cathode, a control electrode, a screen electrode, and an anode; means biasing said anode and screen electrode positively in relation to said cathode whereby current normally flows between said anode and cathode; network means coupled to said anode, screen electrode, and cathode and defining therewith an oscillatory system having a natural period short compared with the period of said wave and having sufficient positive feedback between said anode and screen electrode so that in the absence of other feedback an oscillation rapidly builds up until said anode-cathode current is interrupted; coupling means coupled to said control electrode and oscillatory system and providing negative feedback between said anode and control electrode overbalancing said positive feedback when the control electrode-cathode path in said tube is not conducting and no substantial feedback when said path is conducting, said coupling means including a condenser which is rapidly charged by current flowing through said path when said anode-cathode current is being interrupted and thereafter renders said control electrode negative relative to said cathode; resistance means coupled to said condenser for discharging it at a relatively slow rate, whereby the potential of said control electrode gradually rises relative to that of said cathode and causes said anode-cathode current to rise; and means for applying control pulses to said screen electrode to render said path conducting, whereby the cycle of said saw-tooth wave is completed.

12. An oscillator for generating a saw-tooth wave comprising: an electron tube having a cathode, a control electrode, a screen electrode, and an anode; means biasing said anode `and screen electrode positively in relation to said cathode whereby current vnormally flows between said anode and cathode; network means coupled to said anode, screen electrode, and cathode and defining therewith an oscillatory system having a natural period short compared with the period of said wave and having suflicient positive feedback between said anode and screen electrode so that in the absence of other `feedback an oscillation rapidly builds up until said anode-cathode current is interrupted; coupling means coupled to said control electrode and oscillatory system and providing negative feedback between said anode and control electrode overbalancing said positive feedback when the Acontrol electrode-cathode path in said tube is not conducting and no substantial feedback when said path is conducting, said coupling means including a pair of series-connected condensers between said anode and control electrode which are rapidly charged by current'owing through said path when said anode-cathode lcurrent is being interrupted and thereafter renders said control electrode negative relative to said cathode; resistance means coupled to said condensers for discharging them at a relatively slow rate, whereby the potential of said control electrode, gradually rises relative yto that of said cathode and causes said anode-cathode current to rise until said path again becomes conductive and the rcycle of said wave iscompleted; and means for linearizing said wave including a resistor vconnected between the junction of said condensers- `and said cathode and further including the condenser oi said pair connected to saidanode.` l

References Cited in the le of this patent FOREIGN PATENTS 142,680 Australia Nov; 13,' 1947` 506,856 Great Britain V `Iun e 6, l1939 510,837 Belgium MaylS, 1952 643,993 Great Britain Oct. 4, 19'50l 683,109 

